03.5-04.5 will be a little different than 04.5 up. If the ICP is on the front passenger side valve cover then you have the 04.5 and up. This will have the updated wavy high pressure oil rails.
I'm not a tech by any means but i've been in there a few times.
Injectors are pretty easy to get to. Driver side will require pulling the degas bottle and ficm, passenger side will not require much more than just pulling the valve cover. You can probably get away without replacing the cover gaskets.
You do have to be extremely careful with the seals with the injector R&R and should probably replace the standpipes and dummy plugs if they have not been replaced before, the newer ones have a teflon o ring to help keep them from leaking. I'm sure others can chime in with the real technical details.
Are you sure the injectors themselves are bad. Low voltages can cause a lot of issues. If in fact the injectors are bad you will want to check voltage so that you don't cause the same issues again.